The present invention pertains to an improved tool for tightening a strap around an object or load and adhering the strap onto itself. More particularly, the present invention is directed to a time-out indicator for a pneumatic motor tool for tensioning a strap around a load and welding or melt-adhering the strap onto itself.
Strapping tools are well-known in the art. These tools come in a wide variety of types, from fully manual tools to automatic, table-top tools. These tools are generally specifically designed for use with metal strapping or plastic/polymeric type strapping.
One well known type of strapping tool is a hand-held tool, that can be carried to and from a job-site. When such a tool is configured for use with plastic or polymeric strapping, a pneumatic system is used to vibrate contacting interfacial surfaces of overlapping plastic strap portions. The tool includes a clamping member for anchoring a strap free end portion, and a rotatable feed wheel cooperating with an anvil foot to engage a feed strap portion that is tensioned about the load. A clutch engagably couples the feed wheel to a pneumatic motor which also vibrates a jaw that welds the overlapping strap portions.
An exemplary tool, disclosed in U.S. Pat. No. 5,380,393 to Drabarek et al., also assigned commonly herewith and incorporated herein by reference, discloses a strapping tool having a pneumatic circuit for automatically controlling tool operation, including the timing and duration of strap welding and the cool down period. A pneumatically actuated ram extended after strap tensioning pivots a cam that moves a vibrating weld plate into contact with overlapping strap portions to form the weld. Vibration of the weld plate terminates after a time period controlled by the accumulation of air in a chamber. Air is subsequently bled from a cylinder that counter-pivots the ram to move the welding plate away from the welded strap portions after the cool down period.
As will be recognized by those skilled in the art, known pneumatic strapping tools require many system components that increase the size and weight of the tool. In addition, even though the pneumatic circuit of the above-mentioned U.S. Pat. No. 5,380,393 automates many strapping operations otherwise performed manually, controlling timing of the various tool operations as relatively and precise, and as a result inconsistent strap tension and welds may result.
An improved pneumatic strapping tool is disclosed in pending U.S. patent application Ser. No. 10/171,890, filed Jun. 14, 2002, entitled Dual Motor Strapper, which application is commonly assigned herewith, and the disclosure of which is incorporated herein by reference. In this improved tool, two unidirectional pneumatic motors, one motor for tensioning or feeding strap and another, separate motor for welding the strap material onto itself are provided. To provide flexibility as to operation and maintenance, a self contained modular pneumatic member or module includes pneumatically controlled timing circuits and is readily installed onto and removed from the body and motor portions of the tool.
In this tool, one timing circuit provides for properly timing the xe2x80x9cweldingxe2x80x9d of the strap onto itself. That is, the timing circuit controls the time that the vibrating weld plate is maintained in contact with the overlapping strap portions to form the weld. The timing circuit works, in part, by accumulation of air in a chamber that halts vibration of the weld plate after a predetermined period of time. However, there is currently no indication of the changing state of the circuit. That is, there is no direct indication that the timing circuit has run its course.
Accordingly, there exists a needed for a timing indicator for the pneumatic circuit of a pneumatic strapping tool. Desirably, such an indicator is directly actuated by, e.g., operably connected to, the pneumatic circuit. More desirably, such an indicator provides readily visible indication of the state of the circuit and the weld cycle.
A time-out indicator is configured for use in a pneumatic strapping tool. The toll tensions a strap around a load, adheres the strap onto itself, and cuts a feed end of the strap. The tool has a cylinder housing, a piston disposed within a cylinder in the cylinder housing, a pneumatic weld motor operably connected to the piston, a vibrating weld element operably connected to the piston for contacting the strap and adhering the strap onto itself, and a pneumatic module mounted to the cylinder housing.
The pneumatic module includes a compressed gas inlet, a plurality of valves and passageways between the inlet and the valves to provide compressed gas to the cylinder housing and the pneumatic weld motor. The module further includes at least one timer for operation of the weld motor and for providing pressure to the cylinder. The module further controls timing of the weld motor.
The time-out indicator includes a sleeve fitted into an opening in the module that is disposed above and in communication with the cylinder. The sleeve defines a central, longitudinal opening.
An indicator is biasedly mounted in the sleeve and is disposed for contact with the piston. The indicator reciprocates between a retracted position and an extended position. The indicator indicates a cycle of the strapping tool as an in-cycle state in which the cylinder is under pressure, pressurizing the piston to urge the weld element into contact with the strap and a timed-out state in which the piston is not pressurized.
Preferably, the indicator is in the retracted position when the strapper is in the in-cycle state and is in the extended position, by contact of the piston with the indicator, when the strapper is in the timed-out state.
A seal element is disposed along the stem for preventing the introduction or loss of compressed gas from the pneumatic module. In a current embodiment, the seal is positioned in a seal channel that is defined by a pair of spaced ring walls extending outwardly from the stem.
The sleeve can include an inwardly projecting lip at an upper end thereof. In this configuration, the stem includes an outwardly projecting wall adapted to contact the wall to retain the indicator within the sleeve. The outwardly projecting wall can be one of the ring walls.
A biasing element can be disposed in the sleeve for biasing the indicator to the retracted position. A retaining element is disposed to retain the biasing element in the sleeve. The retaining element can be a spring retaining clip that is received in a grooved formed in an inner wall of the sleeve.
A strapping tool can have the time-out indicator mounted in a pneumatic module for the tool.
These and other features and advantages of the present invention will be apparent from the following detailed description, in conjunction with the appended claims.